Currently, the greatest drawback encountered in mother board manufactures is that, in mounting the add-on cards, after all kinds of the add-on cards are inserted accurately into the PCI slots, a few cards cannot work properly. Only a few cards can work normally, which is the so-called matching problem because not all the add-on cards match with the PCI slots in signal transmission. The main reason of the matching problem is that at PCI bus, no matter the computer signals are command, address, data, etc., the rising edge of the PCI clock is used to latch the computer signals, and if the PCI clock signal deviates from the computer signal, the setup time or holding time obtained by latching the computer signal are insufficient. Further, the design and manufacturing of the system chip set of the mother board are different from those of the chip set of the add-on cards, which makes the matching problem severe and difficult to be solved. The user usually finds the matching problem when the user adds peripheral device, which results in the returning of the computer and the difficulty of repairing service.